An analysis of treatment response in 215 patients treated by percutaneous neprostomy identified obstruction of the urinary tract, complicated by infection and sometimes gram-negative septicemia, as the single most important indication for this intervention. Percutaneous nephrostomy reduced the mortality from gram-negative septicemia from 40%-8%. The length of hospitalization for patients with severe infection complicating urinary tract obstruction was reduced by half in the group undergoing percutaneous nephrostomy. In 43 patients with longstanding obstruction, percutaneous nephrostomy was used to predict recoverable renal function based on the response of renal plasma flow rate to decompression. In 13 patients, percutaneous nephrostomies were used either for the introduction of solvents to dissolve calculi or to serve as pathways for their extraction. Percutaneous nephrostomies in 21 patients were expanded to serve as points of entry for the placement of stent catheters to treat fistulas or bougie cathers to dilate and subsequently catheterize ureteral strictures. While 6 serious complications were encountered, 5 might have been prevented by meticulous adherence to proper technique.